As semiconductors with higher performance and greater integration have been recently developed, market demands for their cost reduction have been stronger. Production lines to assemble such semiconductors require semiconductor chip mounting apparatus with higher throughput and higher precision.
A prior art semiconductor chip mounting apparatus will be described below with reference to FIGS. 9–11 (also see, for example, Patent Publication 1: Japanese Patent Disclosure No. 2000-252305).
FIG. 9 is a perspective view of a semiconductor chip mounting apparatus, FIG. 10 is a schematic operation diagram, and FIG. 11 is a perspective view of a semiconductor chip mounted on a lead frame after the completion of a semiconductor chip mounting process.
As shown in FIG. 9, semiconductor chip mounting apparatus 100 includes semiconductor chip carrier unit 120 and lead frame carrier unit 130. Semiconductor chip carrier unit 120 carries silicon chips 113 from semiconductor chip supply unit 110 to mounting position 150 of tape-like lead frame 131 sent by lead frame carrier unit 130. Lead frame 131 has a predetermined pattern to receive silicon chip 113 at mounting position 150.
Semiconductor chip supply unit 110 is provided with wafer ring 115. Wafer ring 115 is supported by supporting member 114 so that diced silicon wafer 112 lined with dicing sheet 111 can be separated into silicon chips 113 at the time when dicing sheet 111 is expanded. Semiconductor chip supply unit 110 is movable in X1- and Y1-directions to place chips at picking-up position 140 of semiconductor chip carrier unit 120 before starting mounting operations as set forth below.
Semiconductor chip carrier unit 120 is provided with arm 121 that moves to the right and left X1, front and rear Y1, and up and down Z1. Arm 121 includes collet holding unit 122 to the edge of which sucking member 124 is attached. Collet 123 is defined at the low end of sucking member 124 to suck and hold silicon chip 113.
Collet 123 goes and returns along carrier paths y and z as shown in chain lines as arm 121 moves back and forth, and up and down. Lead frame 131 is carried to mounting position 150 of silicon chip 113 by lead frame carrier unit 130 so that silicon chip 113 is mounted on lead frame 131 by arm 121.
As shown in FIGS. 9–11, the semiconductor chip mounting apparatus carries out the following assembling steps. First, semiconductor chip carrier unit 120 is moved to picking-up position 140 and one chip is sucked and held by sucking member 124 from separated silicon chips 113.
Subsequently, semiconductor chip carrier unit 120 is moved to mounting position 150 of lead frame 131 to mount this chip 113 on lead frame 131. Here, since lead frame 131 is heated in advance at a predetermined temperature, silicon chip 113 is fixed on lead frame 131 with an adhesive provided on the back of silicon chip 113.
After being mounted and fixed on lead frame 131, position data of silicon chip 113 at the beginning of mounting, during the mounting and after the completion of mounting are regularly checked as to whether the position data are in predetermined coordinates (X, Y, θ). If the position data are not within a prescribed tolerance, the positions of collet 123 and arm 121 are finely adjusted to optimize picking-up and mounting positions 140 and 150 of semiconductor chip carrier unit 120.
[Prior Art Patent Publication 1]Japanese Patent Disclosure No. 2000-252305 (Page 5 and FIG. 4)
The semiconductor chip mounting apparatus set forth above achieves a high speed operation time of 0.1–0.5 seconds from picking-up one silicon chip 113 to mounting the same on lead frame 131 to reduce its assembling process cost.
With shorter mounting time of silicon chip 113, the temperature of semiconductor chip carrier unit 120 is higher by several tens of degrees than that before such assembling steps and metallic portions of semiconductor chip carrier unit 120 becomes thermally expanded. As a result, picking-up and mounting positions 140 and 150 of semiconductor chip carrier unit 120 are discrepant from those before the mounting step, and mounted silicon chip 113 also deviates from its correct position.
In order to adjust such discrepancies, semiconductor chip mounting apparatus 100 must be tentatively stopped for the adjustment of picking-up and mounting positions of semiconductor chip carrier unit 120. This results in a decline in the throughput of mounting operations.